This invention relates to a device for adjustably limiting the maximum speed of an engine powered hand tool whose speed is controlled by a power-regulating device located in the handle of the tool.
While using engine powered portable hand tools, it is convenient to allow the engine to run at a constant speed that is less than the engine""s maximum speed. By running the engine at a constant speed, the performance of the tool is improved and the load and wear on the engine is reduced. Operator comfort is also increased when the engine is run at a constant speed.
Hand held tools with engine speed limiting devices are available as are hand tools with handles that contain several different buttons to control different functions of the tool. For example, a handle with buttons for steering of the tool is illustrated in EP0968641. The handle described in EP0968641 has a power regulating device and a safety button, but the handle as described in EP0968641 does not allow the operator to limit the speed of the engine in order to make it possible for the operator to run the engine at a constant speed that is less than the maximum speed of the engine.
During use of the hand tool, is it desirable to increase the speed of the engine above the selected speed limit. This could, for example, be required when the amount of grass or bushes to be trimmed by the operator are higher than normal in a concentrated area. In these cases, it is not effective to limit the speed of the engine, and it is necessary to increase the speed of the engine to the maximum speed available to enable the operator to cut the concentrated area.
This invention achieves an increased speed for the engine above a selected speed limit. Under normal operation, an adjustable speed limiting device will stop the power-regulating device at the selected speed. However, if the operator needs to increase the speed of the engine above the selected limit, the operator can accomplish this by exerting an additional force on the power-regulating device. The adjustable speed limiting device will then be deactivated and the speed of the engine will be allowed to increase. The operator may then increase the speed of the engine up to the maximum engine speed.